Funding in the first two cycles of this grant provided support of the Drosophila RNAi Screening Center (DRSC) at Harvard Medical School, allowing us to bring to the community a unique state-of-the art infrastructure for high-throughput RNAi screens (RNAi-HTS) in Drosophila cells. To date, we have facilitated more than 100 full- genome and smaller screens, resulting already in 72 publications on screen results, methods, meta-analysis, etc. DRSC datasets are available for search or download online at our own website, www.flyrnai.org, as well as at other sites such as FLIGHT, GenomeRNAi, FlyMine and most recently, NCBI PubChem BioAssays. Importantly, over the years we have designed, generated, and refined our libraries of double-stranded RNAs (dsRNAs). Our libraries offer exceptional quality and coverage, currently comprising a total of nearly 33,000 unique, high-quality RNAi reagents targeting about 13,500 protein-coding and 400 non-coding Drosophila genes. We also designed and maintain an extensive laboratory information management system (LIMS) and database to track reagents, results, gene information, and more, as well as a website that provides free access to protocols, publications, datasets, software tools, and more. Altogether, we have succeeded in establishing ourselves as an integrated center for screening and technology transfer, serving the widest possible community of researchers. Through support of both on-site and off-site screening using our high-quality libraries, researchers have and are continuing to conduct innovative cell-based assays interrogating diverse functions, such as cell growth, division and death, host-pathogen interactions, signal transduction, cell and organelle size and morphology, and much more. The experience we gained over the past eight years has shaped our view of how to further expand the scope and impact of the DRSC through continued support of on- site and off-site screening as well as rapid transfer of new technologies to the community. In this competing renewal, we seek continued support for the DRSC to keep providing a state-of-the art infrastructure and reagents for functional genomic screening by the widest possible group of researchers. Our effort is critical as, unlike for RNAi screening in mammalian cells, commercial companies have no commitment to provide the community with reagents for Drosophila RNAi screens.